A curtain wall is any exterior wall that is attached to the building structure and which does not carry the floor or roof loads of the building.
In common usage, curtain walls are often defined as thin, usually aluminum-framed walls containing in-fills of glass, metal panels, or thin stone. When you draw the curtain wall, a single panel is extended the length of the wall. If you create a curtain wall that has automatic curtain grids, the wall is subdivided into several panels.
In a curtain wall, grid lines define where the mullions are placed. Mullions are the structural elements that divide adjacent window units. You can modify a curtain wall by selecting the wall and right-clicking to access a context menu. The context menu provides several choices for manipulating the curtain wall, such as selecting panels and mullions.
You can use the default Revit LT curtain wall types to set up curtain walls. These wall types provide 3 levels of complexity, upon which you can simplify or enhance:
Curtain wall types: Curtain Wall 1, Exterior Glazing, Storefront
Sample curtain wall
Sample curtain grid
Sample curtain mullions